Today's industrial manufacturing lines are far more complex and automated than they were only a few years ago. Quite often, hi-tech manufacturing techniques have replaced the more traditional methods previously used. An example of this is the growing use of lasers during component prototyping and high volume manufacturing. Components that were traditionally cut with dies or flame cutters are often made with production lasers.
When these production lasers are used to cut materials of considerable strength or thickness, such as plate steel, the energy level of the laser must be raised to provide the required cutting strength. Unfortunately, as the power level of these lasers increases, so does their size and their cooling requirements. High average power continuous wave (CW) or pulsed gas lasers (such as CO.sub.2) of the type used on product production or processing lines have traditionally been cooled by large forced convection cooling systems. As a result, these laser systems are very large in design and incorporate complex gas-transportation and heat-exchanging systems. In addition to being exceptionally large, these laser systems are very complex in design and incorporate many moving parts, which make these systems very costly to design and install. Besides the one-time cost associated with purchasing and installing these laser systems, they often require constant supervision and a high level of maintenance to keep them operating at peak efficiency. Because of these factors, high power continuous wave or pulsed gas lasers are often unsuitable for a number of applications where mobility, size, weight or freedom from frequent service and maintenance are prime considerations.
In response to this need for lightweight, high powered laser systems, slab laser systems were developed. Slab lasers generally incorporate two or more laser slabs (or plates) which are stacked on top of and spaced apart from each other to form gaps between the slabs. These gaps are filled with a lasing medium, forming a laser cavity, which is excited by applying energy to adjacent slabs to produce a laser beam. There are numerous benefits associated with slab lasers when compared to their pulsed or CW laser forced gas counterparts. Slab lasers are very simple in design, have no moving parts, require little maintenance, and are inexpensive to manufacture.
Concerning slab laser systems, it is well known that by decreasing the size of the gap between the individual slabs, the power output of the individual laser beam being generated between each slab increases. However, there are physical limitations as to how narrow this gap can be made. When the gap becomes too small, the laser beam interacts more intensely with the slabs, which results in the slabs becoming excessively hot. This heating of the slabs substantially reduces the output of the individual laser beams causing a substantial reduction in operating efficiency.
In order to increase the power output of a slab laser system, additional slabs can be stacked upon each other to form additional gaps and produce additional laser beams. These additional laser beams, through the use of mirrors or other reflective devices, can then be combined into a single beam.
However, there are problems associated with these multiple beam slab laser systems. While the numerous laser beams generated between the individual slabs of the slab laser system can be combined into a single output beam, the phase of each of the individual laser beams is not synchronized and, therefore, the single output beam will not be coherent. This can result in the individual laser beams destructively interfering with each other, substantially reducing the focussing ability and uniformity of the single output beam.